The aminoglycoside antibiotics are a valuable therapeutic class of antibiotics which include the kanamycins, gentamicins, streptomycins, sagamicins and the more recently discovered fortimicins. While the naturally produced parent antibiotics are generally, in themselves, valuable antibiotics, chemical modifications have been found to improve the activity, either intrinsic activity or activity against resistant strains or against one or more strains the parent antibiotic is not effective against. Thus, chemical modification has provided both alternative therapeutic agents as well as those which are held in reserve because of the resistance problem. And, because of the development of aminoglycoside-resistant strains and inactivation of the parent antibiotics by R-mediated factors which can develop, the search for new therapeutic entities continues.
Further, some of the naturally produced, parent antibiotics, such as fortimicin B and fortimicin E, are primarily useful as intermediates in preparing derivatives which have more potent antibacterial properties than their weakly active parent antibiotics. The present invention provides two such fortimicins, fortimicins AH and AI.
The fortimicins of this invention are co-produced in the fermentation of Micromonospora olivoasterospora ATCC No. 21819,31009 or 31010 according to the method of Nara et al. U.S. Pat. Nos. 3,931,400 and 3,976,768 which disclose the production of fortimicin A and fortimicin B.
Fortimicins AH and AI are minor factors which are co-produced with fortimicin A, fortimicin B and a number of other minor factors which are the subject of copending commonly assigned patent application Ser. Nos. 025,241; 025,243; 025,247; 025,250; and 025,251, filed of even date herewith and with the minor factors disclosed and claimed in commonly assigned, copending United States patent application Ser. Nos. 863,015 and 863,016, both filed Dec. 21, 1977.